Universal encryption will help terrorists spread their creeds through secure messaging services, according to the FBI.
James Comey, director of the agency, claimed in a blog post that worldwide encryption will help groups like ISIS ahead of his appearance at the Senate Intelligence Committee.
He wrote that secure messaging services and social media will help ISIS recruit new members online.
"When the government's abilitywith appropriate predication and court oversightto see an individual's stuff goes away, it will affect public safety," he wrote on pro surveillance website Lawfare.
"That tension is vividly illustrated by the current ISIL threat, which involves ISIL operators in Syria recruiting and tasking dozens of troubled Americans to kill people, a process that increasingly takes part through mobile messaging apps that are end-to-end encrypted, communications that may not be intercepted, despite judicial orders under the Fourth Amendment."
While he recognised the personal privacy benefits of secure encryption, he added: "My job is to try to keep people safe. In universal strong encryption, I see something that is with us already and growing every day that will inexorably affect my ability to do that job.
"It may be that, as a people, we decide the benefits here outweigh the costs and that there is no sensible, technically feasible way to optimize privacy and safety in this particular context, or that public safety folks will be able to do their job well enough in the world of universal strong encryption."
His comments come after Prime Minister David Cameron denounced encrypted messaging services like Whatsapp earlier this year.
